1. Field of the Invention
The present invention relates to a bioabsorbable pharmaceutical formulation using a lactic acid-glycolic acid copolymer which is excellent as a biodegradable release-sustaining base material for a pharmaceutical formulation.
This application claims priority to JP patent application No. 2005-131893 filed Apr. 28, 2005.
2. Related Background of the Invention
Bioabsorbable pharmaceutical formulations have been designed and developed for: passive targets such as sustained drug efficacy, to alleviate side effects, to reduce the number of administrations of a drug with a short biological half life, and to reduce total dosages, and have been studied often as a means for drug delivery systems. For such a bioabsorbable pharmaceutical formulation, a release sustaining base material, namely a biodegradable polymer is used. For example, Patent Document No. 1 (as listed below) relates to a base material produced by the polycondensation of lactic acid and/or glycolic acid in the presence or absence of a catalyst; and Patent Document No. 2 relates to a method for manufacturing a sustained release type microcapsule using a biodegradable polymer. Various kinds of polymer compounds using lactic acid and glycolic acid have also been studied, for example, Patent Document No. 3 relates to a lactic acid-glycolic acid copolymer which has a weight-average molecular weight of 5,000 or more and 30,000 or less, is free from a catalyst, has a dispersion degree of 1.5 to 2, and has a lactic acid content of 50 to 95 wt % and a glycolic acid content of 50 to 5 wt %; and Patent Document No. 4 relates to a lactic acid-glycolic acid copolymer which has a weight-average molecular weight of 8,000 or more and 15,000 or less, and a ratio of approximately 1.90 or less between a weight-average molecular weight and a number-average molecular weight. Further, Patent Document No. 5 relates to a biodegradable aliphatic polyester which has a content of less than 3.0% for a low molecular polymer having a molecular weight of 1,000 or less.
In addition, Patent Document Nos. 6 and 7 relate to a distribution in molecular weight of a polymer suitable for a release sustaining base material; Patent Document No. 8 relates to a use of a release sustaining formulation using a lactic acid-glycolic acid copolymer (having an intrinsic viscosity of 1.38-0.10); Patent Document No. 9 relates to a method for preparing a release sustaining formulation with a copolymer of lactic acid-glycolic acid (having a molecular weight of 2,000-20,000); and Patent Document No. 10 relates to a use of a release sustaining formulation using a copolymer of lactic acid-glycolic acid (having an intrinsic viscosity of 0.3 or more).
As stated above, referring to a bioabsorbable pharmaceutical formulation and a polymer suitable for its base material, diverse technologies have been disclosed, but there is no pharmaceutical formulation furnished with sufficient performance which prevents an effective drug component from being released rapidly just after the administration of the formulation, thereby allowing continued release of the drug for at least a month at a defined rate. To provide such a formulation is an object of the present invention.
Patent Document No. 1: Publication No. JP S61-28521-A
Patent Document No. 2: Publication No. JP H01-57098-B
Patent Document No. 3: Patent No. JP 3168263 B
Patent Document No. 4: Publication No. JP 2003-206243-A
Patent Document No. 5: Patent No. JP 3254449 B
Patent Document No. 6: Publication No. JP 2004-155792-A
Patent Document No. 7: Publication No. JP 2004-256546-A
Patent Document No. 8: Publication No. JP S57-150609-A
Patent Document No. 9: Publication No. JP S60-181029-A
Patent Document No. 10: Publication No. JP S53-109930-A